Plasma Assisted Combustion: Flame Regimes and Kinetic Studies

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1 Plasma Assisted Combustion: Flame Regimes and Kinetic Studies Yiguang Ju, Joseph Lefkowitz, Tomoya Wada, and Sanghee Won Department of Mechanical and Aerospace Engineering, Princeton University Princeton, NJ 08544, USA AFOSR MURI Program Review

2 MURI Facility Summary and collaborative team structure 3000K Shock Tube (Starikovskiy) 1000K 300K Flame chemistry (Ju, Sutton) Flow Reactors ( Yetter, Adamovich) JSR/Flow reactor Species and kinetics (Ju) MW+laser (Miles) RCM (Starikovskiy) 0.01atm 1atm 100atm

3 Today s Presentation (2014) 1. Plasma activated low temperature combustion & cool flames (liquid fuels: dimethyl ether, n-heptane) 2. Plasma assisted mild combustion (flame regimes) 3. In-situ and time accurate multispecies diagnostics in a plasma flow reactor (kinetics) 4. Development of low temperature and high pressure plasma combustion mechanism (HP-MECH/plasma) (collaboration)

4 Temperature (K) 1. Plasma Activated Low Temperature Combustion and cool flames for liquid hydrocarbon fuels Low temperature ignition Kinetic effect H 2 O 2 =2OH 2HO 2 =H 2 O 2 +O 2 HCO+O 2 =CO+HO 2 CH 2 O+X=HCO+XH R+O 2 =RO 2 RO 2 QOOH R +OH O 2 QOOH R +2OH τ 1 τ 2 Hot ignition Time (sec) Thermal effect dominant H+O 2 =O+OH O+H 2 =H+OH Large molecules Fuel fragments Small molecules Two-stage ignition charateristics >1100 K High temperature ( better understood) K Intermediate K Low Plasma has more kinetic enhancement effect in lower temperature combustion However, poorly studied and understood

1.1 Plasma activated low temperature combustion of liquid fuels: flame regime changes 6x10 5 LTC Temperature 1400K Plasma

CH 2 O PLIF (a.u.) 5x10 5 4x10 5 3x10 5 2x10 5 1x10 5 increase decrease Extinction HTC Hot Ignition 0.00 0.02 0.04 0.06 0.

$12 Fuel mole fraction t 2 t 1 Residence time t 2 << t 1 5 So it occurs in ms or even without an extinction limit!$

5 1.1 Plasma activated low temperature combustion of liquid fuels: flame regime changes 6x10 5 LTC Temperature 1400K Plasma assisted low temperature Flame Extinction LTC LTC Ignition P = 72 Torr, a= 250 1/s, f = 24 khz X O2 =40%, varying X f DME CH 2 O PLIF (a.u.) 5x10 5 4x10 5 3x10 5 2x10 5 1x10 5 increase decrease Extinction HTC Hot Ignition Fuel mole fraction t 2 t 1 Residence time t 2 << t 1 5 So it occurs in ms or even without an extinction limit! P = 72 Torr, a= 250 1/s, f = 34 khz, X O2 =60%, varying X f CH 2 O PLIF (a.u.) 6x10 5 5x10 5 4x10 5 3x10 5 2x10 5 LTC HTC increase decrease 1x10 5 Sun et al. 2014, Combustion & Flame Fuel mole fraction

$fraction, X F$ 0.0125 0.025 0.

$fraction (X O2$ = 0.3) and

6 1.1 Plasma activated low temperature combustion: n-heptane Fuel molar fraction, X F Ignition High Low Flame Extinction Fixed O 2 molar fraction (X O2 = 0.3) and stretch rate (a = 150 s -1 ) Plasma: on Plasma: off Fuel molar fraction, X F

7 OH-PLIF measurement with varied X F (n-heptane) Flame Ignition Hysteresis (S-Curve, thin and thick reaction zones) Flame: Combustion chemistry dominated regime at high temperature and, Ignition: Plasma chemistry dominated regime at low temperature 7

8 Species measurements in plasma assisted low temperature combustion 25.4 mm N-heptane Probe O.D.: 363 µm Adjust position (Vert. & horiz.) Negligible influence on the flame 2/3/2015 Tomoya Wada 8

9 Species distribution near ignition and extinction (X F = 0.1, X O = 0.3, and a = 150 s -1 ) Providing validation targets near extinction near ignition High temperature chemistry Low temperature chemistry

1.2 Experimental study of plasma assisted diffusional cool flames A heated counterflow burner integrated with vaporization system 1 n-heptane/nitrogen vs.

10 1.2 Experimental study of plasma assisted diffusional cool flames A heated counterflow burner integrated with vaporization system 1 n-heptane/nitrogen vs. oxygen/ozone Ozone generator (micro-dbd) produces 2-5 % of ozone in oxygen stream, depending on oxygen flow rate Speciation profiles by using a micro-probe sampling with a micro-gc. 2 Fuel/N 550 K Heated N 550 K Positioning stage Stagnation plane Pressure chamber Micro-GC (a) Cool diffusion flame N 300 K O 2 + O 300 K Ozone generator O 300 K (b) Normal diffusion flame 1) S. H. Won, et al., Combust. Flame 157 (2010) 2) J. K. Lefkowitz, S. H. Won, et al., Proc. Combust. Inst. 34 (2013) 10

11 Stability diagram of diffusional cool flames Lower X f, higher a; no flame initiated. Higher X f, lower a; normal diffusion flames Intermediate X f and lower a; cool diffusion flames Unstable regime extended As increasing both a and X f Continuous ignition and extinction of cool flames Cool flames extends the auto-ignition limit! Strain rate a [s -1 ] % O 3 no flame hot diffusion flame Fuel mole fraction X f 11

12 Sensitivity Analysis near Extinction Reactions Importance of low temperature chemistries RH + OH (~ 15% heat production) R + O 2 reactions (~40%) QOOH reactions HO 2 reactions pc4h9o2=c4h8ooh1-3 c7h15o2-2=c7h14ooh2-3 c7h15o2-4=c7h14ooh4-2 c7h14ooh1-3o2=nc7ket13+oh ch2o+oh=hco+h2o c7h15o2-1=c7h14ooh1-3 c2h5+ho2=c2h5o+oh ho2+oh=h2o+o2 c7h15o2-2=c7h14ooh2-4 c7h15o2-3=c7h14ooh3-5 o3+n2=>o2+o+n2 nc7h16+oh=c7h15-2+h2o X f = 0.05, X O3 = 0.03 T f = 550 K, T o = 300 K Logarithmic senstivity efficient Transport Very sensitive to ozone diffusion O 3 + N 2 O 2 + O + N 2 for initiation of radical pool. Thus, fuel diffusion is important as well. Strong sensitivity to CH 2 O Indicator of low temperature reactivity 1 ch3cho c7h14o2-4 h2o ch2o n2 o2 nc7h16 o3 X f = 0.05, X O3 = 0.03 T f = 550 K, T o = 300 K Logarithmic senstivity efficient 1) S. H. Won et al, Combust. Flame 161 (2014)

13 Speciation Profiles and validation of kinetics Reasonable prediction of acetaldehyde and CH 2 O Significant over-estimation of C 2 H 4 and CH 4 formation Factor of Species mole fraction [ppm] Species mole fraction [ppm] acetaldehyde, exp acetaldehyde, model ch2o, exp ch2o, model Distance from fuel side nozzle [mm] c2h4, exp. c2h4/10, model ch4, exp ch4/10, model (a) (b) Distance from fuel side nozzle [mm] - O2 R + O2 RO 2 QOOH O 2 QOOH Propagation Propagation + O2 Olefin + HO 2 Olefin + HO 2 QO + OH Ketohydroperoxide + OH Branching CH 2 O + R + CO + OH Olefin + C arbonyl + HO 2 13

14 1.3 Plasma assisted premixed cool flames Lean Flammability Limit: Normal flame vs. cool flame Flame speed cool flame? Φ 0 Φ 0 Φ 0 Equivalence ratio 14

15 1.3a. Numerical results of Freely propagating 1D planar cool flames Geometry 1D freely propagating flames S L Mixture and Kinetic model Fuel: Dimethyl ether Oxidizer= (1-x)O 2 + xo 3, x=0-0.1, p=1 atm Ozone chemistry & Dimethyl ether model Ombrello, et al., Combustion and Flame, Vol. 157, 2010 Zhao et al., Int. J. Chem. Kinet., 40 (2008) Liu et al., Combustion and Flame, 160 (2013) Numerical method Modified Chemkin with arc-continuation method Radiation (Optically thin model for CO2, H2O, CO, CH4) Ju et al. JFM,

16 Lean Flammability Limit Extension by formation of cool flames transition Lean limit of ϕ = w & WO 5% ozone addition Ozone promote cool flames Three flame regimes Cool flames significantly extends the lean burn limit of normal flames Cool flames can have a high flame speed between (~15 cm/s) 16

Experimental observation of premixed cool flames N 2 @ 600 K Heated N 2 @ 600 K Positioning stage Stagnation plane N 2 @ 300 K DME+ O 2 + O 3 @ 300 K

17 Experimental observation of premixed cool flames N 600 K Heated N 600 K Positioning stage Stagnation plane N 300 K DME+ O 2 + O 300 K Pressure chamber Micro-GC Ozone generator O 300 K Temperature of N 2 = 600K Temperature of DME/O 3 /O 2 =300 K Strain rate=80 s -1 Ozone concentration: 3% 17

18 Premixed Cool Flame stability/regime diagram Three flame regimes found: Unburned mixture past lean limit Stable cool flames Transition regime to hot flame Lean limit slightly increases with strain Width of stable cool flame region doubles from 75 s -1 to 85 s -1 18

$mole fraction in diluted air Can plasma extend the boundary of mild combustion to lower$

19 2. Plasma assisted mild combustion Diluted air Temperature T ig T pig High temperature combustion T ig Conventional combustion Conventional Mild combustion New plasma assisted mild combustion (PAMiC) m T f Unstable combustion region 21% 10% 3% Oxygen mole fraction in diluted air Can plasma extend the boundary of mild combustion to lower temperature?

20 1. Electrodes 2. Insulation 3. Preheat burner 4. Oxidizer flowing sec. Mild combustion: co-axial burner Plasma 1 2 Electrode Preheated Oxidizer 4 4 Plasma reactor Center burner 3 Center burner (Fuel/N 2 ) Plasma reactor (lean mix.) 6/27/2014 Tomoya Wada (Princeton University) 20

21 MILD combustion w/ and w/o plasma Condition Preheat gas temp.: 1050 K Preheat gas O 2 : 12% Center burner vel.: 20 m/s Center burner CH 4 /N 2 : 10% Plasma reactor vel.: 5 m/s Plasma reactor CH 4 /air ratio: 0% and 3% Shorter and wider reaction zone 6/27/2014 Tomoya Wada (Princeton University) 21

(CH4/O2) 250 CH2O Experiment Vacuum Chamber

Model Reactor CH 2 O 0 0 5 10 15 20 Time

Wavelength (nm) Wavenumber (cm -1 ) Line

22 3. In Situ time accurate Mid-IR LAS Diagnostics in plasma/flow reactors (CH4/O2) 250 CH2O Experiment Vacuum Chamber Mole Fraction (ppm) CH2O Model Reactor CH 2 O Time (ms) Collimating Lenses Mirror Ge Etalon Flip Mirror CH2O, Quartz Wall CH4, H2O, C2H2 Macor Wall Species Fig. 1 CH 2 O time history measurements and modeling of a 300 pulse burst at 30 khz in a stoichiometric CH 4 /O 2 /He with 75% dilution. Wavelength (nm) Wavenumber (cm -1 ) Line 300 K (cm/molecule) CH 4 /Temp x x10-22 CH 2 O x10-20

23 Continuous Plasma CH 4 /O 2 /He Mole Fraction (ppm) Stoichiometric, 75% helium dilution, 30 khz pulse rep. freq. Fuel consumption and major species agree well with model Disagreement with minor species CH2O Experiment CH2O Model CH3OH Experiment CH3OH Model C2H2 Experiment C2H2 Model C2H4 Experiment C2H4 Model C2H6 Experiment C2H6 Model Intermediate species Mole Fraction (ppm) Mole Fraction (ppm) x O2 Experiment O2 Model CH4 Experiment CH4 Model 175 H2O Experiment H2O Model CO Experiment CO Model CO2 Experiment CO2 Model H2 Experiment H2 Model Frequency (Hz) Frequency (Hz) Frequency (Hz)

24 CH 2 O + H + O 6% CH 3 + H 2 O + O 2 + M 94% CH 3 O 2 + M CH 3 + OH CH 3 O + O 2 /OH CH 3 OH + O 2 + OH 15% CH 4 + e - 13% CH 3 + H CH 2 OH + H CH O 2 100% CH 2 O + HO 2 + O 2 100% CH 4 + O 2 + CH H + e - 100% CH 2 + H/H 2 + O 2 100% CO + OH + H CO 2 + H + H CO 2 + H 2 CH 2 O + O Figure 6: Path flux analysis of fuel consumption integrated over a single pulse period during continuous discharge at 30 khz repetition frequency and steady state temperature conditions. Bold species represent those which are measured in Figure 5, red arrows refer to reactions from the combustion model, and blue arrows are from the plasma model. Large uncertainty in low temperature oxidation pathways

25 In Situ Mid-IR Diagnostics and kinetic study in plasma/flow reactors (c2h4/o2) In-situ Steady state species measurements Mole Fraction (ppm) C2H2, Exp. C2H2, HP C2H2, USC 100 CH4, Exp. CH4,HP CH4, USC H2O, Exp. H2O, HP H2O, USC 1 T, Exp. T, HP T, USC Time from last pulse (ms) Temperature (K) Fig. 2 Comparison of measured and predicted species (H2O, CH4, C2H2 formation in C2H4 oxidation: HP-Mech vs. USC Mech

26 Ethylene Oxidation Pathways (C2H4/O2/Ar) + OH 15% C2H4 + Ar(+) 13% C2H3+ + O2 100% CH2CH2OH LTC O2C2H4OH 100% 2 CH2O + OH + H +M 31% C2H5 HTC + O 11% + Ar* 5% + O 13% + H 21% H + CH2CHO CH3+ HCO + O 21% + O2 46% + e- 30% + e- 65% C2H2 C2H + O2 100% HCO + CO + O2 + M 85% + O2 + M 97% C2H5O2 C2H5O2H + HO2 98% CH20 + HCO M = Third body collider X = Radical CO + CH2O + OH Blue = Plasma Red = High temperature, Green= Low temperature PAC activates C2H4 low temperature chemistry CH3O2 + X 95% CH3O CH2O + X 96% Large uncertainty in low temperature oxidation pathways

27 Key reaction pathways in combustion kinetics at high pressure and low temperature: HO2/RO2 CH 2 O blue arrow: Below 700K; yellow arrow: K; red: above 1050K Strong spectra overlap between HO2, H2O2, RO2 in UV and with H2O in mid-ir Unstable OH detection is limited by linebroading. Bretfield et al., JPC letters, 2013.

28 New diagnostics: HO 2 /OH using mid-ir Faraday Rotational Spectroscopy V ( RMS ν) ( GP0 sin 2θ) +B field = Θ RMS Laser Lock-In Amplifier Paramagnetic (radical) species Absorption HO 2 energy levels Zeeman splitting ν Dispersion ν

29 Experimental results: HO 2 /OH measurements Signal Sensitivity HO2 OH DME flow reactor model validation Implication: RO2 QOOH O2QOOH uncertainty HCO+O2=HO2+CO reaction uncertainty and HCO formation pathway? Bremfield et al., 2013, JPC letters, 2013; Kurimoto et al. 2014

30 4. High Pressure Mechanism for Plasma Assisted Combustion (HP-Mech/plasma) H2/H2O2/O3/CO/CH2O/CH3OH/CH4 Base mechanism: high pressure combustion mechanism: HP-Mech H2/O2 sub-mechanism: Burke et al (PU and ANL) CO/CH2O/CH3OH sub-mechanism: Labbe et al (ANL and PU in CEFRC) O3 sub-mechanism: (PU, Ombrello et al. 2010) O3 decomposition updated (J. Michael, 2013) O(1D) reaction pathways O(1D) + Fuels/N2/O2/CO/CO2/H2O/CH2O updated CH 3 OH Mole Fraction 1.2E E E E E K and 2.5 atm 1368 K and 2.4 atm 1458 K and 2.3 atm O2(singlet) reaction pathways O2(singlet) + Fuels/H/OH/CH3/H2/CH4 updated NOx reaction pathways Mueller et al., Intl. J. Chem. Kin. (1999), Vol. 31, pp Allen et al., Combust. Flame (1997), Vol. 109, pp Dean and Bozelli (2000, Gardiner ed.) Klippenstein, Stephen J.; Harding, Lawrence B.; Glarborg, Peter; Miller, James (2011) 2.0E E Time [μs] 1610 K and 2.2 atm

31 Tests of NO x chemistry in various fuel oxidation systems 1.2% 1.0% H 2 Mole Fraction 0.8% 0.6% 0.4% 0.2% 0.0% H 2 system 1.0 atm 3.0 atm 0 Time 1 [s] 2 CO Mole Fraction 0.6% 0.5% 0.4% 0.3% 0.2% 0.1% 0.0% CO system 3.0 atm Time [s] NO Mole Fraction 1.E-04 8.E-05 6.E-05 4.E-05 2.E-05 0.E Time [s] T ini = 807 K 1% H 2, 2% O 2, 108 ppm NO, balance N 2 Experimental measurements at various points in flow reactor (Mueller et al., 1999) NO / NO 2 Mole Fraction 1.E-04 8.E-05 6.E-05 N 4.E-05 2.E-05 NO 0.E Time [s] T ini = 952 K 0.5% CO, 0.75% O 2, 0.5% H 2 O, 108 ppm NO, balance N 2 Experimental measurements at various points in flow reactor (Mueller et al., 1999) Mueller et al., Int. J. Chem. Kin. 31 (1999), pp Collaborating with Richard Yetter, 2014

32 Plasma Modeling Tool Development ZDPlasKin CHEMKIN II - SENKIN ρρ ddyy kk dddd = ωω kkww kk 1 γγ 1 kk dd(nntt gggggg ) BB dddd = PP eeeeee PP eeeeeeee PP ccheeee 32 E/N 0 Time

33 HP-Mech/plasma validation: Ozone effect on flame speeds Increase of flame speed, % 14% 12% 10% 8% 6% 4% 2% O3-2330ppm-expts O3-2330ppm-expts O3-2330ppm-HPMech O3-3730ppm-HPmech Konnov-Simulation-3730ppm Konnov-Simulation-2330ppm 0% Equivalence ratio

34 Conclusions 1. This MURI program is a very exciting exploration of knowledge frontier. 2. Plasma activated Self-Sustaining diffusion and premixed Cool Flames & mild combustion were established for the first time. Creating exciting opportunities in engine and fuel applications. 3. Plasma has a strong kinetic effect in low temperature combustion. A direct ignition transition to flame without extinction limit was observed. 4. New diagnostic method (e.g. FRS) for in-situ and time accurate measurements of intermediate species and HO2 radicals was developed. Plasma active low temperature chemistry via CH2O and RO 2 is an important fuel oxidation pathway at low temperature. 5. Plasma combustion chemistry remains a big challenge, especially at low temperature. The existing plasma kinetic mechanism is not able to predict appropriately the plasma activated low temperature kinetics.

35 Journal Publications Awards: Publications and Awards: 1. Ju, Y. and Sun, W., (2015), Plasma Assisted Combustion: Dynamics and Chemistry, Progress of Energy Science and Combustion, Ju, Y. and Sun, W., (2015), Plasma Assisted Combustion: Challenges and Opportunities, Combust. Flame, Invited opinion paper. 3. Peng Guo; Timothy Ombrello, Sang Hee Won, Christopher A Stevens, John L Hoke, Frederick Schauer, Yiguang Ju, Schlieren Imaging and Pulsed Detonation Engine Testing of Ignition by a Nanosecond Repetitively Pulsed Discharge, submitted to Combust. Flame, Lefkowitz, J.K., Uddi, M., Windom, B., Lou, G.F., Ju, Y. (2015), In situ species diagnostics and kinetic study of plasma activated ethylene pyrolysis and oxidation in a low temperature flow reactor, Proceedings of Combustion Institute, 35, Won, S.H., Jiang, B., Diévart, P., Sohn, C.H., Ju, Y., (2015), Self-Sustaining n-heptane Cool Diffusion Flames Activated by Ozone, Proceedings of Combustion Institute, 35, Brumfield, B., Sun, W., Wang, Y., Ju, Y., and Wysocki, G. (2014), Dual Modulation Faraday Rotation Spectroscopy of HO2 in a Flow Reactor, Optics Letters, Vol. 39, Issue 7, pp (2014). 1. Distinguished Paper Award of the 35th International Symposium on Combustion: Self-Sustaining n-heptane Cool Diffusion Flames Activated by Ozone 2. Plenary Lecturer, The 8th International Conference on Reactive Plasmas, Fukuoka, Japan, 2014.

36 5. Future research Plasma combustion kinetic mechanism development Time accurate species and plasma property measurements Low temperature Fuel oxidation kinetics involving O(1D), HO2, O3, O2(1Δ) in photolysis and flow reactor (0.1-2 atm) High pressure plasma assisted cool flames (1-10 atm)

38 3. Plasma assisted low temperature combustion Methane vs. Dimethyl ether (DME) P = 72 Torr f = 24 khz Laser beam OH, CH 2 O PLIF 25.4 mm Peak Voltage = 7.8 KV E = 7500 V/cm, E/N ~ 900 Td Power ~ 17 W (repetitive pulses) 38

1 Plasma assisted normal and cool diffusion flames DME/O 2 /O 3 Direct chemi-luminescence image of cool premixed flame

39 1. Plasma assisted Cool Flames and Mild Combustion: (a) Hot diffusion flame N-heptane Normal diffusion flame T f ~1900 K Heated N 2 (b) Cool diffusion flame Cool diffusion flame T f ~650 K Fig. 1 Plasma assisted normal and cool diffusion flames DME/O 2 /O 3 Direct chemi-luminescence image of cool premixed flame by ICCD camera for DME/O 2 /O 3 mixture (φ = 0.104) Fig.2 Plasma assisted cool premixed flame (DME) Fig.3 Plasma assisted mild combustion (methane diluted by N2)

1. Plasma activated Cool Flames: n-heptane-air 2400 (a) Hot diffusion flame T f ~1900 K Maximum temperature T max [K] 2000 1600 1200 800 nc 7 H 16 /N 2 vs O 2 or O 2 /O 3 in counterflow burner X f =

40 1. Plasma activated Cool Flames: n-heptane-air 2400 (a) Hot diffusion flame T f ~1900 K Maximum temperature T max [K] nc 7 H 16 /N 2 vs O 2 or O 2 /O 3 in counterflow burner X f = 0.05,T f = 550 K, and T o = 300 K HTI LTI Extinction limit of conventional hot diffusion flame (HFE) without O 3 CF branch with O 3 HF branch Extinction limit of cool diffusion flame (CFE) T f ~650 K Strain rate a [s -1 ] Fig. 2 Ozone (red line) extends the burning liit of cool flames (b) Cool diffusion flame Fig. 1 Hot and cool n-heptane diffusion flames at the same condition Plasma makes cool flame to be observed at 1 atm at 10 ms timescale. Strain rate a [s -1 ] no flame Fuel mole fraction X f hot diffusion flame Fig. 3 Diagram of hot flame (pink), stable cool flame (blue), and unstable cool flame (white)

1050 K (including 12% O 2 ) Center burner CH

: 10-70% and 5-40 m/s Flame structure change

41 2. Plasma assisted flameless (MILD) combustion 1. Electrodes 2. Insulation 3. Preheat burner 4. Oxidizer flowing sec. 1 2 w/o Plasma Tested conditions Preheat: 1050 K (including 12% O 2 ) Center burner CH 4 /N 2 and vel.: 10-70% and 5-40 m/s Flame structure change with CH4% in plasma reactor 0% 3% 70% w/ Plasma 0% 3% 70% Flameless combustion Regular combustion

42 Fig. 3 OH and HO2 diagnostics in DME flow reactor by using Faraday rotational spectroscopy. Predicted and measured signals. 3. In Situ Mid-IR Diagnostics and kinetic study in plasma/flow reactors Diluents Oxidizer Fuel Diluents Detector QCL Laser Heated Vacuum Chamber Detector Ge Etalon Collimating Lenses Electrode Beam Splitter Vacuum Pump Oscilloscope Nanosecond - Pulsed Power Supply Observation Window Pulsed Signal Generator Digital Delay Generator Function Generator Mole Fraction (ppm) C2H2, Exp. C2H2, HP C2H2, USC 100 CH4, Exp. CH4,HP CH4, USC H2O, Exp. H2O, HP H2O, USC 1 T, Exp. T, HP T, USC Time from last pulse (ms) Fig. 2 Comparison of measured and predicted species (H2O, CH4, C2H2 formation in C2H4 oxidation: HP-Mech vs. USC Mech Temperature (K) Fig. 1 Experimental setup of plasma reactor and IR-Herriot cell In situ diagnostics of H2O, CH4, C2H2, OH, and HO2 measurements were conducted by using mid-ir absorption and FRS.

43 4. Development of high pressure mechanism (HP-Mech) for plasma assisted combustion Increase of flame speed, % 14% 12% 10% 8% 6% 4% 2% 0% O3-2330ppm-expts O3-2330ppm-expts O3-2330ppm-HPMech O3-3730ppm-HPmech Konov-Simulation-3730ppm Konov-Simulation-2330ppm Equivalence ratio Fig.1 Comparison of predicted flame speed increase (percentage) by O3 addition in methane/air flame (HP-Mech vs. Konov)

2009 MURI Topic #11: Chemical Energy Enhancement by Nonequilibrium Plasma Species

2009 MURI Topic #11: Chemical Energy Enhancement by Nonequilibrium Plasma Species Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion Program Overview